Signaling system



Feb. 7, 1933. O, E BUCKLEY 1,896,767

S IGNALING SYSTEM y /A/VE/VTOA OE. BUC/(LEV ATTORNEY Feb. 7, 1933.

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PERCENT CHANGE OFRESSTANCE R PERCENT CHANGE OF /NDUCTANCE L o. E. BUCKLEY 1,896,767

SIGNALING SYSTEM Filed June 29, 1931 2 Sheets-Sheet 2 -m srMME rR/cAL POLAR/Z4 T/o/vfr/cs l Afvoa) o so @4 uNsrMMET/g/:AL PoLAn/zAr/o/v (F1a. 2) so A cum/E A MMF ou: To o/RECT CURRENT G^USS /NVENTOR A T TORNE Y 0.5 Buc/LEY tude.

Patented Feb. 7, 1933 l OLIVER nBUcxLEY, or MAPLEWOOD, NEW .JERsEmAssIGNoitTo iaELL TELEPHONE LABORATORIES, INCORPORATEDpOF NEW- YORK, Y., A CORPORATION OF l Application filed .Tune 29,

lThis invention relates toV signaling systems and particularly to inductance and other coils employed in such systems. l An object of the invention is to reduce hystereticlosses in magnetic materials forming the cores of inductance and Asimilar coils.

Another object of the invention is to reduce resistance losses in coils comprising cores of magnetic materials. f i

' A, further obiect of the invention Vis to so condition magneticmaterials that they may besubjected to valternating and direct current fields encountered in signaling without suffering serious impairmentsV of their etliciency. A more specific object of the invention is to secure constancy in the inductance presented to alternating current by magnetic cores employed in signaling. v f

It has been found that thereexists a need in signaling systems, particularly in telephone systems, for coils whose inductance and resistance do not varv with current ampli? This applies particularlyto carrierV current loading coils and filter' coils Where the variations introducedby'the non-linear magnetic characteristics of the core materialvintroduce cross-talk and modulationdiiiiculties between the diii'erent signaling channels." At present air core coils are used, since no known magnetic material has suiciently constant permeability to prevent modulation effects.

A means'which hasfrequently been proposed in the past to secure constancy of inductance for alternating currentis to mag-- netize the core material 'With a Vsteady mag-V netizing force much larger than and superposed on the alternating magnetizing force. The magnetic material is thus partly Asaturated with the resultvthat the permeability over a. small range of alternating magnetizing force is reduced and made morenearly constant, while at the same time the'liysteresis loss is reducedl l In accordance with the principles 'of this invention, the objects stated above are attained by subjecting the magnetic'material, when in use in a signalingsystem, and when itis consequently under the effect of an alternating or fluctuating magneticiel'd, to an SIGNAL-ING SYSTEM i' 1931i.l serial No. 547,689."

additional( unidirectional and. This, enrl directional or steady magnetization may be accomplished, either bv a direct current' lo-`wing through anadditional winding provided on'the core of'magnetic material7 or bya permanentm'agnet suitably disposed in /proxim-V itv tothe core.'v gFurthermore, the steady magnetization maybe applied, either symmetrically with respect to an aXis intersecting the alternating current windings or 'diss symmetrically with respect to said aXis.

be reduced; It has been found that theinsertion oia` suitable` devicefsucli asa two-electrode vacuum tubeV Working at filament saturation into the direct current circuitcreates an impedance sufficiently highto prevent the flow of appreciable alternating current theres` If.. use is made of a dissymmetrical magnetizas in and consequently the provision of such a device is an important feature of this inven-v tion.

Among the `magnetic materials which haveV beeniound to be particularly `suitable for the purposes of the present invention, como`sitions containing from about 30%v to 81/2 nickeljand the balance iron are partic- Y ularly f adapted. These materials have a much lower hysteresis loss in relation to'their permeability when nearly saturated than doesV -ironor other vrelatively hard magnetic ma'- teri'als. They possess the further advantage of requiring only averysmall magnetizing lforce to magnetize them nearly to saturation Consequently, the steady' magnetization `may be accomplished by a permanent magnet suitably disposed. As a material for the permanentmagnet,cobalt steel has been found to'be suitable. i Y i Speciiic embodiments ofthe present invention willnow be described and a comparivson will bemade between fourftypes vof-cores,

to wit, unpolarized and polarized cores on the onehand;l and symmetrically polarized 100 discussionfbelow of the principles of opera-v rtionofthis invention.

. Y n'ying drawings, in which Fig. 1 serves to illustrate both the unpolarized type and the symmetrically polarized of core;

' gig. 2 shows a type of a dissymrnetrically Y Y will be "used herein. In this eX" ression i .i

Jequals27rf,

alternating current; L isjthe inductancejand polarized core;

` Fig. 3 shows a different embodiment .of a

symmetricallypolarized core in which a magnet madeof permanent magnet steelk is used for supplying the steady symmetrical magnetization; and Y i Figs 4, i- A and 5 represent various curves to which reference will be made during the X Referring Vmore particularly to: Fig. 1, transformer core having the form shown and Acomprising about' v70-laminations i006.

inch (.1521nillimeteri) thickness in the outer members and140laminations in the inner member of aV magneticV material containing about 7 81/2% nickel, 1.7%.chromium and the balance `iron is` provided .with alternating vcurrent windingsvl and 14, respectively, and

with a direct current winding which latter is arranged symmetrically withl respecty ,to

. maybe supplied A steady .magnetizing current y to the coil 15 bythe battery 10'." A source of alternating'current 11 supan aXis {cf-jy.

plies alternating current of about cycles l per second Vto the windings 13 and 14. Measuring devices 16 and 16 are provided for measuring the direct and alternating current magnetizing forces, respectively. VVa- VVriableresistances 17 and. 17 serve for the-purpose Vof varying the direct and alternating magnetizing forces, respectively. Windings -13candf14 are connected inY series and wound inthe samedirection. In (this manner no alternatingmagneto-motive force is produced in the center limb of the magnet core since any 'HuX caused by one of the windings and tending toiow through thecente'r limb is opposed and neutralized `byran opposing fluxzof the same-magnitude caused by the other winding.

Anunpolarized core structure 1s constituted lby, an` arrangement such as the one,v

shown in Fig. 1 in which the switch 9 in the ldirect current circuit is left open. By suitably'adjusting and varying the resistancel the core 10 offFig. 1 wassubjected to an al# fternatingV magnetizing force' which was ,vai ried from .0003 gauss to .005 gauss, while the'.l direct currentcircuit was open. The variations of the inductance L and of the revsistance R of thevr alternating l'current circuit Yare graphically represented as functionsof,A the varying magneto-motive force duetothe '-variation of the alternatingcurrent in curves A and B of Figs. 4V and 44A, respectively.

For theV small range of alternating current magnetization mentioned Y' (.0003 to .005

-.g auss) the inductance L increased 11% and the resistance increased 135%. `As astand# ard of comparison of the efficiency as inductance stabilizers of the various coilstructures under different conditions of operation, the

expression ma Q .where f isr` the frequencyof the R is the resistance of the alternating current circuit. For high values of constancy of iny ductance the factor Q should also be high, and theV higher Q the better the efficiency vorA the core as an inductance stabilizer. When the direct current circuit was "open, the mathenetizing .force was Vvariedv from .0003 to .005 gauss and the magnetic permeability of the material varied from 5980 to 6550.

l The core vwas then treated byy closing theA direct current circuit and applying a direct niagnetizing force of onel gauss upon its center member; simultaneously, the alternating magnetizing torce was varied for thecon- Sider-able range of from .0004 to .lgauss As` isl shown-bycurves C and D of Vigs. 4` and 44A, for this largefchange of magnetization L and R vincreased only 2 andV 5%,

respectively. Similarly, if calculated andeXf pressed in values of Q, this decreased from' 74.5v but was stabilized at the Vconsiderablr-r value of 31, as compared-to the change from 24.9 to 9.9 inthe previous case. The magnetic permeability varied' 'from 8470V tod8r65 j over this range.

w In orderto determinethe relative merits .Y of symmetrically and dissymmetrically magerencfe to Fig.2 in `which those reference 'numerals which are identical 'with those of Fig. 1- indicate parts similar tothose of Fig.

high impedance, to wit, in the particularenibodimenty shown, a two-electrode tungsten lilament vacuum tube 20 which is preferably .adjusted to operate in a condition of voltage Y. f

saturation,'i. e., a condition such Athat the whole of therelectron emission fromfthe filament is utilized as thek plate current, and consequently an increase of the, plate` voltage.

vwillno longer increase the ynumber of elec- .Y

`trons emitted per unit of time." In a practical y embodiment ofk the dissymmetrically polarized core of this modification, the direct vcurrent magnetizing force ywas varied from zero ynetized cores, investigations *wereY carriedfout which will be describedwith particular refto about one gauss while the alternating current magnetization was kept at a constant value of about 0.005 gauss. For these increasing values of direct magnetization, Q increased from 20.1 to 29.8` only; see curve A of Fig. 5 and the permeability of the core material varied from 7020 to 788 when the direct current magnetizing force was varied from 0 to 1 gauss. f

Next, the direct current magnetizing force of the symmetrically polarized core of Fig. 1` was varied between the same limits as in the case of. the dissymmetrically polarized core, i. e., between 0 and about 1 gauss and the alternating magnetization was kept at the same constant value as in the previous test. The variation of Q is shown in curve B, Fig. 5. It is seen that Q increased from 20 to 82 as compared with an increase from 20.1 to 29.8 for curve A; this corresponds to a decrease in the magnetic permeability of fromv 7050 to 788 with increasing direct current magnetization. Y

In the embodiment of the invention represented by Fig. 3, a permanent steel bar. magnet made of steel having a high coercivity Y was used to symmetrically polarize a core of magnetic material of the same composition as that mentioned above. The permanent magnet was placedY in the center'limb of the core in a manner to polarize the core in the same manner and direction as the direct current winding of Fig. 1. It produced a direct magnetizing force of .18 gauss. Whenthe alternating current magnetizing force was changed from .0002 gauss to .0034 gauss, L increased 1.28% and R increased 24%. Q decreased from 41.7 but was stabilized at the rather high value of 28 for this range of magnetizing force. The permeability increased from 3220 to 3260 when the magnetizing force was changed from .0002 gauss to .0034 gauss.

It was thus ascertained that the magnetic stability during operation of'inductance and other coils may be improved by the application of a polarizing eld thereto, and that a higher value of magnetic stability may be obtained if the polarizing field is applied symmetrically with respect to an axis passing through the operating winding or windings and the center of gravity of the core.

While the methods of the present invention have been applied successfully inparticular to signaling systems including cores of magnetic material containing about 7 81/2% nickel, 1.7% chromium and the balance iron, the invention `is-not limited to the use of this particular material but magnetic materials of other compositions may also be benefited by this treatment.

VVhatis claimed is 1. A signaling system comprising va coil substantially free of modulation characteristics having a core of magnet-ic material,

core to a unidirectional magnetic field, said Y instrumentalities being independent of the winding Icarrying the alternating current. 2. System as defined in claim 1, characterized in this that the impedance stabilizing means comprises instrumentalities for apply-v ing a magnetic `polarizing field which is symmetrical with respect to an axis passing through said winding carrying the alternatof said core.

- 3. System as defined in 4claim 1characterized in this that the impedance stabilizing means are located dissymmetrically with respect to an axis intersectingtheY winding and the'center of gravity of the core.

4. System as defined in claim 1, characterl 'seV ' ing current and through the centerof gravity l ized in this that the impedance. stabilizing means comprises a permanent magnet suitl ably arranged to magnetize said core. y

5. System as defined in claim 1,"characterized in this that the impedance stabilizing means comprises a separate winding upon the core of magnetic material in addition to that carrying the alternating current, said winding being connected in series with a source oi direct current and with an element having a high impedance, whereby the flow of alternating current in said direct current winding is minimized. i v i 6. In a signaling system comprising a coil yhaving a core of magneticmaterial andv a winding traversed by the signaling currents, a circuit includingv a source of current for applying a unidirectional magnetizing field to said core, said circuit including a two-electrode -space discharge device having a high impedance, whereby the signaling currents are prevented from flowing in the direct current circuit.

7. A driving source of alternating electro-` motive force, a load receiving current from said source and at the same frequencies, a regulating device connected between said source and said load, said device having a stabilizedimpedance to flow of said current, said f regulating device comprising a winding assop ciated with a core and means for steadily, magnetizing the core to anearly saturated condition such that the magnetic characteris- 

